The present invention relates to improved methods and devices for sensing temperature and other physical fields, based on the effect of the physical field on the relative distribution of the intensity of interrogating light between two distinct components of an optical light guide. The physical fields covered by this invention include, in addition to temperature, anything which can cause a change in said relative distribution, including infrared radiation and the spatial distribution thereof.
The term "thermal sensing" as used in this application has a broad coverage. It covers the sensing of a thermal condition, like temperature, or any agent or process which can produce a temperature change, including as examples infrared radiation and exothermic chemical reactions.